using UnityEditor;
using UnityEngine;
using System.IO;

namespace gay.lilyy.TextureStitcher
{
  [CreateAssetMenu(fileName = "TextureStitcherSettings", menuName = "Texture Stitcher/Settings")]
  public class TextureStitcherSettings : ScriptableObject
  {
    public Texture2D[] textures;
    public string savePath = "Assets/StitchedTexture.png";
  }

  [CustomEditor(typeof(TextureStitcherSettings))]
  public class TextureStitcherEditor : Editor
  {
    private SerializedProperty texturesProp;
    private SerializedProperty savePathProp;

    private void OnEnable()
    {
      texturesProp = serializedObject.FindProperty("textures");
      savePathProp = serializedObject.FindProperty("savePath");
    }

    public override void OnInspectorGUI()
    {
      serializedObject.Update();

      EditorGUILayout.LabelField("Texture Layers (Top → Bottom)", EditorStyles.boldLabel);
      EditorGUILayout.PropertyField(savePathProp);

      DrawReversedArray(texturesProp);

      GUILayout.Space(10);

      if (GUILayout.Button("Generate Stitched Texture"))
        GenerateStitchedTexture();

      serializedObject.ApplyModifiedProperties();
    }

    private void DrawReversedArray(SerializedProperty array)
    {
      if (!array.isArray)
        return;

      // Draw size field (normal Unity behavior)
      EditorGUILayout.PropertyField(array.FindPropertyRelative("Array.size"));

      // Reverse array in-place
      int count = array.arraySize;
      for (int i = 0; i < count / 2; i++)
        array.MoveArrayElement(i, count - 1 - i);

      // Draw array normally
      EditorGUILayout.PropertyField(array, GUIContent.none, true);

      // Restore original order
      for (int i = 0; i < count / 2; i++)
        array.MoveArrayElement(i, count - 1 - i);
    }

    private void GenerateStitchedTexture()
    {
      TextureStitcherSettings settings = (TextureStitcherSettings)target;
      GenerateStitchedTexture(settings);
    }

    internal static void GenerateStitchedTexture(TextureStitcherSettings settings)
    {
      int width = 0;
      int height = 0;

      foreach (var tex in settings.textures)
      {
        if (!tex) continue;
        width = Mathf.Max(width, tex.width);
        height = Mathf.Max(height, tex.height);
      }

      Texture2D output = new Texture2D(width, height, TextureFormat.RGBA32, false);
      Color[] pixels = new Color[width * height];
      for (int i = 0; i < pixels.Length; i++) pixels[i] = Color.clear;

      output.SetPixels(pixels);

      // Bottom → top
      for (int i = 0; i < settings.textures.Length; i++)
      {
        var tex = settings.textures[i];
        if (!tex) continue;

        Texture2D resized = Resize(tex, width, height);
        Color[] src = resized.GetPixels();
        Color[] dst = output.GetPixels();

        for (int p = 0; p < dst.Length; p++)
        {
          Color s = src[p];
          dst[p] = Color.Lerp(dst[p], s, s.a);
        }

        output.SetPixels(dst);
      }

      output.Apply();
      File.WriteAllBytes(settings.savePath, output.EncodeToPNG());
      AssetDatabase.Refresh();

      Debug.Log("Stitched texture saved to " + settings.savePath);
    }

    private static Texture2D Resize(Texture2D src, int width, int height)
    {
      RenderTexture rt = RenderTexture.GetTemporary(width, height, 0);
      Graphics.Blit(src, rt);

      RenderTexture.active = rt;
      Texture2D result = new Texture2D(width, height, TextureFormat.RGBA32, false);
      result.ReadPixels(new Rect(0, 0, width, height), 0, 0);
      result.Apply();

      RenderTexture.active = null;
      RenderTexture.ReleaseTemporary(rt);
      return result;
    }
  }
}